WARSAW, Poland (CNS) — Catholic leaders in Poland and Ukraine pledged mutual forgiveness for the deaths of tens of thousands of civilians during World War II.

Archbishop Sviatoslav Shevchuk of Kiev-Halych, head of the Ukrainian Catholic Church, and Archbishop Jozef Michalik of Przemysl, president of the Polish bishops’ conference, asked forgiveness and also appealed to all Ukrainians and Poles in the world “to open their hearts and minds bravely to mutual forgiveness and reconciliation.”

“Neither violence nor ethnic cleansing can ever be a method of solving conflicts between neighboring peoples or nations, or justified on political, economic or religious grounds,” said the church leaders’ joint statement, published June 28 in Warsaw.

The statement was timed to commemorate the 1943-44 massacres in Volhynia and eastern Galicia, in which up to 100,000 Poles and Ukrainians were killed by rival sides under Nazi occupation.

It said the 70th anniversary was an opportunity for “coming closer as brothers” on the basis of truth “which does not embellish or leave out anything.”

“Tens of thousands of innocent people became victims of crime and ethnic cleansing; among them women, children and the elderly, mostly Poles, but also Ukrainians and those who rescued their endangered neighbors and relatives,” the statement said.

“An objective understanding of the facts and a revelation of the size of the tragedies and dramas of the past is becoming an urgent task for historians and specialists. It is only the learning of historical truth that can calm the emotions which have grown around this issue.”

Around 80,000 Poles were murdered in 1943-44 by fighters with the Ukrainian Insurgent Army in an ethnic cleansing campaign to clear non-Ukrainians from what would become Ukraine.

Dozens of Catholic priests were killed and churches burned during the atrocities, which peaked in July and August 1943. Polish self-defense groups in various regions retaliated with the murder of up to 30,000 Ukrainians, although numbers are disputed.

Catholic bishops from both countries began discussions in 1987 and urged reconciliation in a 2005 joint letter from the Polish bishops’ conference and Ukrainian Catholic Synod of Bishops.